Image sensor and imaging device including the same

ABSTRACT

An imaging device includes a pixel array with first and second pixels respectively having first and second conversion gains connected to row and column lines; a row driver determining a selection row line among the row lines; a readout circuit obtaining first and second pixel signals from first and second pixels connected to the selection row line; a column driver generating first and second image data from the first and second pixel signals; and an image signal processor using the first and second image data to generate an object image. The second pixels include an expansion capacitor connected between a floating diffusion node and a ground node. Exposure time of the first pixels is equal to or longer than exposure time of the second pixels. An area of a light receiving region of the first pixels is equal to an area of a light receiving region of the second pixels.

CROSS-REFERENCE TO RELATED APPLICATION(S)

A claim of priority under 35 U.S.C. § 119 is made to Korean PatentApplication No. 10-2020-0016900 filed on Feb. 12, 2020 in the KoreanIntellectual Property Office, the entirety of which is herebyincorporated by reference.

BACKGROUND

The present disclosure relates to image sensors and imaging devicesincluding the same.

Image sensors receive light and generate electric signals responsivethereto, and may be made of semiconductor material. As the computer andcommunications industries continue to advance, there has become anincreasing demand for image sensors having improved performance. Suchsemiconductor-based image sensors may include for example charge coupleddevice (CCD) image sensors and complementary metal-oxide-semiconductor(CMOS) image sensors. Among CCD image sensors and CMOS image sensors,the driving methods of CMOS image sensors are typically straightforwardand simple. Also, CMOS image sensors include signal processing circuitsthat may be integrated into a single chip. Accordingly, since CMOS imagesensors may be miniaturized, the use of CMOS image sensors is rapidlyincreasing. Recently, there has been interest in various methods forimproving noise characteristics, dynamic range, and the like of imagesensors.

SUMMARY

Embodiments of the inventive concepts provide an image sensor having ahigh dynamic range (HDR) and an imaging device including the same.

Embodiments of the inventive concepts provide an imaging deviceincluding a pixel array connected to a plurality of row lines and aplurality of column lines, and including a plurality of first pixelshaving a first conversion gain and a plurality of second pixels having asecond conversion gain, lower than the first conversion gain; a rowdriver determining a selection row line from among the plurality of rowlines; a readout circuit respectively obtaining a first pixel signal anda second pixel signal from first pixels and second pixels connected tothe selection row line; a column driver generating first image data fromthe first pixel signal and second image data from the second pixelsignal; and an image signal processor generating an object image fromthe first image data and the second image data. Each of the secondpixels includes a floating diffusion n ode, a ground node, and anexpansion capacitor connected between the floating diffusion node andthe ground node. The row driver sets exposure time of the first pixelsto be equal to or longer than exposure time of the second pixels. Anarea of a light receiving region of each of the first pixels is equal toan area of a light receiving region of each of the second pixels.

Embodiments of the inventive concepts further provide an imaging deviceincluding a pixel array including a plurality of color pixel groups,wherein each of the plurality of color pixel groups including aplurality of first pixels and at least one second pixel; an image datagenerator that exposes the plurality of first pixels during a firstexposure time to generate first image data, exposes the at least onesecond pixel during the first exposure time to generate second imagedata, and sequentially exposes the plurality of first pixels and the atleast one second pixel during a second exposure time to generate thirdimage data; and an image signal processor that merges the first imagedata, the second image data, and the third image data, to generate anobject image. The image data generator generates the first image data bysumming pixel signals obtained from the plurality of first pixels.

Embodiments of the inventive concepts still further provide an imagesensor including a plurality of first pixels including a first floatingdiffusion region disposed in a substrate and a plurality of firstphotodiodes connected to the first floating diffusion region; at leastone second pixel including a second floating diffusion region disposedin the substrate and at least one second photodiode connected to thesecond floating diffusion region, the second floating diffusion regionis disposed adjacent to the first pixels in a direction parallel to anupper surface of the substrate; and an expansion capacitor disposed inthe substrate and connected to the second floating diffusion region by ametal line. The expansion capacitor has a region overlapping at leastone first pixel among the plurality of first pixels in a directionparallel to the upper surface of the substrate.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features, and advantages of the inventiveconcepts will be more clearly understood from the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates a view of an imaging device according to embodimentsof the inventive concepts.

FIG. 2 illustrates a view of a pixel array of an image sensor accordingto embodiments of the inventive concepts.

FIGS. 3A and 3B illustrate views respectively of pixel arrays of imagesensors according to embodiments of the inventive concepts.

FIG. 4 illustrates a view of a pixel group that may be respectivelyincluded in the pixel arrays of FIGS. 3A and 3B.

FIG. 5A illustrates a circuit diagram of a low-illuminance pixel of animage sensor according to an embodiments of the inventive concepts.

FIG. 5B illustrates a circuit diagram of a high-illuminance pixel of animage sensor according to embodiments of the inventive concepts.

FIGS. 6A and 6B illustrate views respectively of a sampling operation ofa low-illuminance pixel and a sampling operation of a high-illuminancepixel.

FIG. 7 illustrates a plan view of the pixel group of FIG. 4 according toembodiments of the inventive concepts.

FIG. 8A illustrates a cross-sectional view taken along line I-I′ of FIG.7.

FIG. 8B illustrates a cross-sectional view taken along line II-II′ ofFIG. 7.

FIG. 9 illustrates a plan view of the pixel group of FIG. 4 according toembodiments of the inventive concepts.

FIG. 10A illustrates a cross-sectional view taken along line of FIG. 9.

FIG. 10B illustrates a cross-sectional view taken along line IV-IV′ ofFIG. 9.

FIG. 11 illustrates a view of a pixel array of an image sensor accordingto embodiments of the inventive concepts.

FIG. 12 illustrates a view of a pixel group that may be included in thepixel array of FIG. 11.

FIG. 13 illustrates a plan view of the pixel group of FIG. 12 accordingto embodiments of the inventive concepts.

FIG. 14A illustrates a cross-sectional view taken along line V-V′ ofFIG. 13.

FIG. 14B illustrates a cross-sectional view taken along line VI-VI′ ofFIG. 13.

FIG. 15 illustrates a plan view of the pixel group of FIG. 12 accordingto other embodiments of the inventive concepts.

FIG. 16A illustrates a cross-sectional view taken along line VII-VII′ ofFIG. 15.

FIG. 16B illustrates a cross-sectional view taken along line VIII-VIII′of FIG. 15.

FIG. 17 illustrates a plan view of the pixel group of FIG. 12 accordingto other embodiments of the inventive concepts.

FIG. 18 illustrates a view of a pixel group that may be included in thepixel array of FIG. 11.

FIG. 19 illustrates a plan view of the pixel group of FIG. 18.

FIG. 20A illustrates a cross-sectional view taken along line IX-IX′ ofFIG. 19 according to embodiments of the inventive concepts.

FIG. 20B illustrates a cross-sectional view taken along line IX-IX′ ofFIG. 19 according to other embodiments of the inventive concepts.

FIG. 21 illustrates a flowchart of an operation method of an imagingdevice according to embodiments of the inventive concepts.

FIG. 22 illustrates a waveform diagram of the operation method of FIG.21.

FIG. 23 illustrates a flowchart of an operation method of an imagingdevice according to embodiments of the inventive concepts.

FIG. 24 illustrates a waveform diagram of the operation method of FIG.23.

FIG. 25 illustrates a block diagram of an electronic device including animaging device according to embodiments of the inventive concepts.

DETAILED DESCRIPTION

Hereinafter, embodiments of the inventive concepts will be described indetail with reference to the accompanying drawings. The same referencenumerals may be used for the same components in the drawings, andduplicate description of the same components may be omitted.

As is traditional in the field of the inventive concepts, embodimentsmay be described and illustrated in terms of blocks which carry out adescribed function or functions. These blocks, which may be referred toherein as units or modules or the like, are physically implemented byanalog and/or digital circuits such as logic gates, integrated circuits,microprocessors, microcontrollers, memory circuits, passive electroniccomponents, active electronic components, optical components, hardwiredcircuits and the like, and may optionally be driven by firmware and/orsoftware. The circuits may, for example, be embodied in one or moresemiconductor chips, or on substrate supports such as printed circuitboards and the like. The circuits constituting a block may beimplemented by dedicated hardware, or by a processor (e.g., one or moreprogrammed microprocessors and associated circuitry), or by acombination of dedicated hardware to perform some functions of the blockand a processor to perform other functions of the block. Each block ofthe embodiments may be physically separated into two or more interactingand discrete blocks without departing from the scope of the inventiveconcepts. Likewise, the blocks of the embodiments may be physicallycombined into more complex blocks without departing from the scope ofthe inventive concepts.

FIG. 1 illustrates a view of an imaging device according to embodimentsof the inventive concepts.

Referring to FIG. 1, an imaging device 10 may include an image sensor100 and an image signal processor (ISP) 200.

The image sensor 100 may be implemented to detect an object to generatea pixel signal, and to use the generated pixel signal to generate anobject image. The image sensor 100 may include a pixel array 110, a rowdriver 120, a readout circuit 130, a column driver 140, and a timingcontroller 150. The row driver 120, the readout circuit 130, the columndriver 140, and the timing controller 150 as taken together may forexample be characterized as an image data generator.

The pixel array 110 may include a plurality of pixels PX arranged in anarray form along a plurality of row lines and a plurality of columnlines.

Each of the plurality of pixels PX may include a photoelectricconversion element. For example, each of the plurality of pixels PX mayinclude a photodiode generating charge in response to an optical signalincident from an external source, and a pixel circuit generating anelectrical signal corresponding to the charge generated by thephotodiode.

In addition, each of the plurality of pixels PX may include a pixelcircuit for generating a pixel signal from the charge generated by thephotodiode. The pixel circuit may include a floating diffusion (FD), areset transistor, a driving transistor (source follower), a selecttransistor, and a transfer transistor.

The pixel circuit may obtain a pixel signal by detecting a reset voltageand a pixel voltage from each of the plurality of pixels PX andcalculating a difference therebetween. The pixel signal may correspondto an amount of the charge generated by the photodiode included in eachof the plurality of pixels PX.

The row driver 120 may drive the pixel array 110 in a row unit (e.g., byunits of row). For example, the row driver 120 may generate atransmission control signal that controls the transfer transistor of thepixel circuit, a reset control signal that controls the reset transistorof the pixel circuit, and a selection control signal that controls theselect transistor of the pixel circuit.

The readout circuit 130 may convert an analog pixel signal generatedfrom the pixel array 110 into a digital signal, and may output theconverted digital signal. The readout circuit 130 may include a samplingcircuit and an analog-to-digital converter (ADC).

The sampling circuit may include a plurality of samplers such ascorrelated double samplers (CDS). The plurality of samplers may beconnected through column lines to pixels connected to a row lineselected by the row driver 120, and may detect a reset voltage and apixel voltage from the pixels. In some examples, the plurality ofsamplers may compare each of the reset voltage and the pixel voltagewith a predetermined ramp voltage, and may output the result of thecomparison.

The analog-to-digital converter (ADC) may convert the pixel signalobtained from the reset voltage and the pixel voltage detected by theplurality of samplers into a digital signal, and may transfer theconverted digital signal to the column driver 140.

The column driver 140 may include a latch or buffer circuit, anamplification circuit, and the like, and may temporarily store thedigital signal. The column driver 140 may process the digital signalreceived from the readout circuit 130. For example, the column driver140 may output image data corresponding to a column line selected from aplurality of column lines, among digital signals, to the image signalprocessor 200.

The timing controller 150 may control operation timing of the imagesensor 100. For example, the timing controller 150 may control operationtiming of the row driver 120, operation timing of the readout circuit130, or operation timing of the column driver 140.

In an embodiment, the timing controller 150 may control the operationtiming of the image sensor 100 differently according to an operationmode. For example, in a first operation mode, the timing controller 150may control the row driver 120 such that a plurality of pixels aresequentially exposed. In the first operation mode, the timing controller10 may automatically set exposure time of the plurality of pixels. Inaddition, in a second operation mode, the timing controller 150 maycontrol the row driver 120 such that a pixel for high-illuminance and apixel for low-illuminance are simultaneously exposed. Hereinafter, apixel for high intensity of illumination may be defined as ahigh-illuminance pixel, and a pixel for low intensity of illuminationmay be defined as a low-illuminance pixel.

The low-illuminance pixel may refer to a pixel having a first conversiongain, and the high-illuminance pixel may refer to a pixel having asecond conversion gain that is smaller than the first conversion gain.The high-illuminance pixel may include an expansion capacitor connectedto a floating diffusion node. The expansion capacitance may expand(increase) the capacitance of the floating diffusion node of thehigh-illuminance pixel to be more or greater than the capacitance of afloating diffusion node of the low-illuminance pixel. Other than theexpansion capacitor, the size and the characteristics of thelow-illuminance pixel and the high-illuminance pixel may be the same.For example, an area of a light receiving region of the low-illuminancepixel may be the same as an area of a light receiving region of thehigh-illuminance pixel.

The image signal processor 200 may be implemented to process the imagedata output from the readout circuit 130. For example, the image signalprocessor 200 may perform signal processing operations such as forexample color interpolation, color correction, gamma correction, colorspace conversion, edge correction, and the like on received frame data,to generate image data. The image signal processor 200 may process theimage data to generate an object image, and may transmit the objectimage to a display or may store the object image in a memory. In anembodiment, the image signal processor 200 may merge first image dataobtained from the low-illuminance pixel and second image data obtainedfrom the high-illuminance pixel, to generate an object image.

An imaging device 10 according to an embodiment of the inventiveconcepts may simultaneously expose a low-illuminance pixel and ahigh-illuminance pixel to acquire low-illuminance image data andhigh-illuminance image data, and may merge the acquired low-illuminanceimage data and the acquired high-illuminance image data to generate anobject image, to remove various noises and to secure a high dynamicrange.

The plurality of pixels PX included in the pixel array 110 may begrouped by predetermined number to form a plurality of pixel groups. Inan embodiment, the plurality of pixel groups may be color pixel groupshaving a red-green-green-blue (RGGB) pattern or a red-green-blue-white(RGBW) pattern.

FIG. 2 illustrates a view of a pixel array of an image sensor accordingto embodiments of the inventive concepts.

Referring to FIG. 2, a pixel array 200 may include a plurality of pixelgroups PG connected to a plurality of row lines ROW[1] to ROW[m] and aplurality of column lines COL[1] to COL[n].

Each of the plurality of pixel groups PG may be implemented to obtain adifferent color image. In an embodiment, each of the plurality of pixelgroups PG may include at least one color filter to pass specificwavelengths of light. For example, each of the plurality of pixel groupsPG may include any one of a red color filter, a green color filter, or ablue color filter. Further, each of the plurality of pixel groups PG mayinclude any one of a cyan filter, a yellow filter, or a magenta filter.As a result, the plurality of pixel groups PG may form a predeterminedcolor pattern on the pixel array 200. Hereinafter, a structure of thepixel array 200 will be described in more detail with reference to FIGS.3A to 4.

FIGS. 3A and 3B illustrate views respectively of pixel arrays of imagesensors according to embodiments of the inventive concepts. FIG. 4illustrates a view of a pixel group that may be respectively included inthe pixel arrays of FIGS. 3A and 3B.

Referring first to FIG. 3A, a red-green-green-blue (RGGB) pattern may beformed in a pixel array 300 by using first to fourth pixel groups 310 to340 adjacent to each other. Each of the first and fourth pixel groups310 and 340 may include a plurality of green color pixels G1 to G4, thesecond pixel group 320 may include a plurality of red color pixels R1 toR4, and the third pixel group 330 may include a plurality of blue colorpixels B1 to B4. In FIG. 3A, each of the first to fourth pixel groups310 to 340 may include four pixels adjacent to each other, but thenumber of pixels included in each of the pixel groups may be variouslymodified differently.

Each of the first and fourth pixel groups 310 and 340 may include atleast one green color filter. The green color filter may be provided foreach of the plurality of pixels G1 to G4, or at least a portion of theplurality of pixels G1 to G4 may be provided to share one green colorfilter.

The second pixel group 320 may include at least one red color filter.The red color filter may be provided for each of the plurality of pixelsR1 to R4, or at least a portion of the plurality of pixels R1 to R4 maybe provided to share one red color filter.

The third pixel group 330 may include at least one blue color filter.The blue color filter may be provided for each of the plurality ofpixels B1 to B4, or at least a portion of the plurality of pixels B1 toB4 may be provided to share one blue color filter.

Specific pixel configurations of each of the first to fourth pixelgroups 310 to 340 may be as illustrated in FIG. 4.

Referring to FIG. 4, a pixel group 500 may include four pixels (e.g.,PXa and PXb) having a 2×2 matrix structure. In an embodiment, at leastone pixel, among a plurality of pixels included in the pixel group 500,may be a high-illuminance pixel, and the remaining pixels thereof may below-illuminance pixels. For example, as illustrated in FIG. 4, the pixelgroup 500 may include one high-illuminance pixel PXb and threelow-illuminance pixels PXa.

Capacitance of a floating diffusion region of the high-illuminance pixelPXb may be larger than capacitance of a floating diffusion region of thelow-illuminance pixel PXa, due to the high-illuminance pixel PXbincluding an expansion capacitor Cext. As a result, the high-illuminancepixel PXb such as shown in FIG. 4 may accumulate more charges than alow-illuminance pixel (e.g., any one of PXa in FIG. 4). Therefore, in acase that an image sensor operates in a high dynamic range (HDR) mode,since charge loss may be prevented even when exposure time of thehigh-illuminance pixel PXb is controlled to be the same as exposure timeof the low-illuminance pixel PXa, image data having a relatively highresolution and a relatively high dynamic range may be acquired.

An expansion capacitor Cext may be disposed in a pixel circuit region ofthe high-illuminance pixel PXb. In an embodiment, the expansioncapacitor Cext of the high-illuminance pixel PXb may overlap at least aportion of a low-illuminance pixel (e.g., any one of PXa in FIG. 4), ona plane parallel to a substrate.

In an embodiment, the expansion capacitor Cext may for example include ametal-insulator-metal (MIM) capacitor. The MIM capacitor may have astructure in which a dielectric film is disposed between an upperelectrode and a lower electrode which are formed of a conductivematerial. In some examples, the dielectric film may include a materialhaving a high dielectric constant. For example, the dielectric film mayinclude AlN, BN, Zr₃N₄, ZrO₂, HfO₂, or the like.

In an embodiment, the expansion capacitor Cext may for example include apoly-insulator-poly (PIP) capacitor. The PIP capacitor may have astructure in which an oxide film is disposed between an upperpolysilicon film and a lower polysilicon film. In some examples, theoxide film may be formed by oxidizing the lower polysilicon film.

In an embodiment, the expansion capacitor Cext may for example havecapacitance of 1 fF or more and less than 1 pF. Depending on thecapacitance, the expansion capacitor Cext may extend to the pixelcircuit region of a low-illuminance pixel.

The high-illuminance pixel PXb may have the same size andcharacteristics as the low-illuminance pixel PXa, except that thehigh-illuminance pixel PXb further includes an expansion capacitor Cextconnected to the floating diffusion region. For example, the area of thelight receiving region of the high-illuminance pixel PXb may be the sameas the area of the light receiving region of the low-illuminance pixelPXa. Since the image sensor may use pixels PXa and PXb having the samesize and characteristics to generate image data, a dark current causedby a difference in size and characteristics for each pixel may beremoved, and noise may be reduced.

As illustrated in FIGS. 3A and 4, a predetermined color pattern may beformed using four 2×2 pixel groups 500 including a total of 16 pixels ina pixel array, and such a pixel arrangement structure may be referred toas a tetra-structure. Alternatively, a predetermined color pattern maybe formed using four 3×3 pixel groups including a total of 36 pixels ina pixel array, and such a pixel arrangement structure may be referred toas a nona-structure.

In other embodiments, a red-green-blue-white (RGBW) pattern may beformed in a pixel array instead of the red-green-green-blue (RGGB)pattern as shown in FIG. 3A.

Referring to FIG. 3B, an RGBW pattern may be formed in a pixel array 400by using first to fourth pixel groups 410 to 440 adjacent to each other.The first pixel group 410 may include a plurality of green color pixelsG1 to G4, and the second pixel group 420 may include a plurality of redcolor pixels R1 to R4. In addition, the third pixel group 430 mayinclude a plurality of blue color pixels B1 to B4, and the fourth pixelgroup 440 may include a plurality of white color pixels W1 to W4. InFIG. 3B, each of the first to fourth pixel groups 410 to 440 may includefour pixels adjacent to each other, but the number of pixels included ineach of the pixel groups may be variously modified differently.

The first pixel group 410 may include at least one green color filter.The green color filter may be provided for each of the plurality ofpixels G1 to G4, or at least a portion of the plurality of pixels G1 toG4 may be provided to share one green color filter.

The second pixel group 420 may include at least one red color filter.The red color filter may be provided for each of the plurality of pixelsR1 to R4, or at least a portion of the plurality of pixels R1 to R4 maybe provided to share one red color filter.

The third pixel group 430 may include at least one blue color filter.The blue color filter may be provided for each of the plurality ofpixels B1 to B4, or at least a portion of the plurality of pixels B1 toB4 may be provided to share one blue color filter.

The fourth pixel group 440 may include at least one white color filter.The white color filter may be provided for each of the plurality ofpixels W1 to W4, or at least a portion of the plurality of pixels W1 toW4 may be provided to share one white color filter.

FIG. 5A illustrates a circuit diagram of a low-illuminance pixel of animage sensor according to embodiments of the inventive concepts, andFIG. 5B illustrates a circuit diagram of a high-illuminance pixel of animage sensor according to embodiments of the inventive concepts.

Referring first to FIG. 5A, a low-illuminance pixel PXa may include aphotodiode PD and a pixel circuit. The pixel circuit may include afloating diffusion FD, a reset transistor RX, a driving transistor DX, aselect transistor SX, and a transfer transistor TX.

When an optical signal output from a light source is reflected from anobject and is incident on a pixel array, the photodiode PD may generatecharge in response to incident light. The charge generated by thephotodiode PD may be stored in the floating diffusion FD.

When the reset transistor RX is turned on by a reset control signal RG,a voltage of the floating diffusion FD may be reset to a power supplyvoltage VDD. When the voltage of the floating diffusion FD is reset, theselect transistor SX may be turned on by a selection control signal SG,to output a reset voltage to a column line COL through a pixel node PN.

When the transfer transistor TX is turned on by a transfer controlsignal TG after the reset voltage is output to the column line COL, acharge generated by the photodiode PD may move to the floating diffusionFD.

The driving transistor DX may operate as a source-follower amplifierthat amplifies the voltage of the floating diffusion FD. When the selecttransistor SX is turned on by the selection control signal SG, a pixelsignal corresponding to an amount of the charge generated by thephotodiode PD may be output to the column line COL through the pixelnode PN.

In some embodiments the low-illuminance pixel PXa may also include aplurality of photodiodes, instead of just a single photodiode PD asshown in FIG. 5A. The plurality of photodiodes may share a floatingdiffusion FD and a reset transistor RX. In addition, charges generatedby the plurality of photodiodes may be accumulated in the floatingdiffusion FD. When a select transistor SX is turned on by a selectioncontrol signal SG, a pixel signal corresponding to the total amount ofcharge generated by the plurality of photodiodes may be output to acolumn line COL through a pixel node PN.

Referring to FIG. 5B, a high-illuminance pixel PXb may include aphotodiode PD and a pixel circuit such as described with respect to FIG.5A. Different than the low-illuminance pixel PXb of FIG. 5A, thehigh-illuminance pixel PXb may further include an expansion capacitorCext. Since the high-illuminance pixel PXb has the same configurationand operation principle as the low-illuminance pixel PXa, except forfurther including an expansion capacitor Cext, a duplicate descriptionof like configuration and operation will be omitted from the followingdescription of FIG. 5B.

The expansion capacitor Cext in FIG. 5B may be connected between thefloating diffusion FD node and a ground node to increase capacitance ofthe floating diffusion FD. In some embodiments, the expansion capacitorCext may be a metal-insulator-metal (MIM) capacitor or apoly-insulator-poly (PIP) capacitor, and may have capacitance of 1 fF ormore and less than 1 pF.

FIGS. 6A and 6B illustrate views respectively of a sampling operation ofa low-illuminance pixel and a sampling operation of a high-illuminancepixel.

Referring first to FIG. 6A, charges e⁻ overflowed from a photodiode PDmay be generated in a high-illuminance environment. Since capacitance ofa floating diffusion FD region of a low-illuminance pixel may belimited, when a low-illuminance pixel is used in a high-illuminanceenvironment, charge loss may occur, and noise may occur in image data.

Referring to FIG. 6B, capacitance of a floating diffusion FD region of ahigh-illuminance pixel may be increased by an expansion capacitor Cext,as compared to the case of FIG. 6A which does not include an expansioncapacitor. Therefore, even when charges e⁻ overflowed from a photodiodePD may be generated in a high-illuminance environment, since theoverflowed charges may be accommodated in the floating diffusion FDregion, charge loss may not occur.

Due to these characteristics, an image sensor according to an embodimentof the inventive concepts may generate low-illuminance image data usinglow-illuminance pixels, may generate high-illuminance image data usinglow-illuminance pixels, and may merge the low-illuminance image datawith the high-illuminance image data to generate an object image.

FIG. 7 illustrates a plan view of the pixel group of FIG. 4. FIG. 8Aillustrates a cross-sectional view taken along line I-I′ of FIG. 7, andFIG. 8B illustrates a cross-sectional view taken along line II-IP ofFIG. 7.

Referring first to FIG. 7, a pixel group 700 may include first to fourthphotodiodes PD1 to PD4, first to fourth transfer gate electrodes TG1 toTG4, and first and second floating diffusion regions FDa and FDb.

The first transfer gate electrode TG1 may be a gate electrode of a firsttransfer transistor connected to the first photodiode PD1, and thesecond transfer gate electrode TG2 may be a gate electrode of a secondtransfer transistor connected to the second photodiode PD2. In addition,the third transfer gate electrode TG3 may be a gate electrode of a thirdtransfer transistor connected to the third photodiode PD3, and thefourth transfer gate electrode TG4 may be a gate electrode of a fourthtransfer transistor connected to the fourth photodiode PD4.

The first to fourth photodiodes PD1 to PD4 may configure differentpixels. In an embodiment, the first to third photodiodes PD1 to PD3 mayconstitute low-illuminance pixels, and the fourth photodiode PD4 mayconstitute a high-illuminance pixel.

In order to increase resolution of an image sensor, a size and full wellcapacitance of individual pixels may be decreased. The full wellcapacitance may be a performance index indicating a dynamic range of theimage sensor. As the full well capacitance of individual pixels isdecreased, a blurring phenomenon may occur, and thus an image quality ofthe image may deteriorate. In order to prevent deterioration of theimage quality, the image sensor may share a floating diffusion regionbetween adjacent pixels to secure an appropriate dynamic range.

The first to third photodiodes PD1 to PD3 constituting thelow-illuminance pixel may be commonly connected to the first floatingdiffusion region FDa. For example, the first to third photodiodes PD1 toPD3 may share the first floating diffusion region FDa. The first tothird photodiodes PD1 to PD3 may share the first floating diffusionregion FDa, to combine pixel signals of each of the low-illuminancepixels at an analog stage.

Also, the fourth photodiode PD4 constituting the high-illuminance pixelmay be connected to the second floating diffusion region FDb.

FIG. 7 illustrates the first and second floating diffusion regions FDaand FDb disposed at a center of the pixel group 700, but positions ofthe first and second floating diffusion regions FDa and FDb may bevariously modified. For example, the floating diffusion region of eachof the first to fourth photodiodes PD1 to PD4 may be disposed at acenter of each of the first to fourth photodiodes PD1 to PD4. In thiscase, the floating diffusion region of each of the first to thirdphotodiodes PD1 to PD4 may be connected to each other through a metalline.

An expansion capacitor Cext may be disposed below the fourth photodiodePD4. The expansion capacitor Cext may be connected to the secondfloating diffusion region FDb to increase capacitance of the secondfloating diffusion region FDb. In some embodiments, the expansioncapacitor Cext may be a metal-insulator-metal (MIM) capacitor or apoly-insulator-poly (PIP) capacitor, and may have capacitance of 1 fF ormore and less than 1 pF. In an embodiment, the expansion capacitor Cextmay overlap at least a portion of the first to third photodiodes PD1 toPD3, on a plane parallel to a substrate.

The cross-section taken along line I-I′ of FIG. 7 may be as illustratedin FIG. 8A.

Referring to FIG. 8A, a pixel group 700 may include a first photodiodePD1, a first color filter CF1 disposed on the first photodiode PD1, asecond photodiode PD2, a second color filter CF2 disposed on thephotodiode PD2, an element isolation layer 710, a pixel circuit region730, and a first floating diffusion region FDa.

The element isolation layer 710 may electrically isolate a first pixelregion including the first photodiode PD1 and a second pixel regionincluding the second photodiode PD2. The element isolation layer 710 mayelectrically isolate the first pixel region and the second pixel regionto prevent crosstalk due to optical interference. The element isolationlayer 710 may extend from lower surfaces of micro-lenses ML1 and ML2 tobe disposed between the plurality of pixel regions in a verticaldirection.

The element isolation layer 710 may for example be formed using a trenchprocess, a local-oxidation-of-silicon (LOCOS) process, or the like. Whenthe element isolation layer 710 is formed by using a trench process, theelement isolation layer 710 may have a deep-trench-isolation (DTI)structure or a shallow-trench-isolation (STI) structure. In anembodiment, the element isolation layer 710 may extend from the lowersurfaces of the micro-lenses ML1 and ML2 to an upper surface of thepixel circuit region 730, to have a full-deep-trench-isolation (FDTI)structure fully isolating a plurality of pixel regions.

The pixel circuit region 730 may include a first transfer gate electrodeTG1, a second transfer gate electrode TG2, and a plurality of metallines.

When a first transfer transistor is turned on according to a controlsignal input to the first transfer gate electrode TG1, a chargegenerated by the first photodiode PD1 may move to the first floatingdiffusion region FDa. In addition, when a second transfer transistor isturned on according to a control signal input to the second transfergate electrode TG2, a charge generated by the second photodiode PD2 maymove to the first floating diffusion region FDa.

The first floating diffusion region FDa may store the charges generatedby the first photodiode PD1 and the second photodiode PD2. For example,the charge generated by the first photodiode PD1 in a first pixel regionand the charge generated by the second photodiode PD in a second pixelregion, in response to an optical signal incident from an externalsource, may be stored in the first floating diffusion region FDa.

The first micro-lens ML1 may be disposed on the first color filter CF1,and the second micro-lens ML2 may be disposed on the second color filterCF2. The first micro-lens ML1 may focus an optical signal transmittedfrom an object onto the first photodiode PD1. In addition, the secondmicro-lens ML2 may focus an optical signal transmitted from an objectonto the second photodiode PD2.

The first pixel region including the first photodiode PD1 and the secondpixel region including the second photodiode PD2 may constitutedifferent pixels. In an embodiment, the first pixel region and thesecond pixel region may constitute low-illuminance pixels, and may sharea first floating diffusion region FDa. Also, the first pixel region andthe second pixel region may constitute the same color pixel region. Forexample, when the first color filter CF1 and the second color filter CF2are red color filters, the first pixel region and the second pixelregion may constitute a red pixel.

FIG. 8A illustrates a case in which the color filters CF1 and CF2 andthe micro-lenses ML1 and ML2 are provided on the first photodiode PD1and the second photodiode PD2, respectively. However, upper structuresof the first photodiode PD1 and the second photodiode PD2 may bemodified in various ways. For example, one color filter and onemicro-lens may be arranged on the first photodiode PD1 and the secondphotodiode PD2.

The cross-section taken along line II-II′ of FIG. 7 may be asillustrated in FIG. 8B.

Referring to FIG. 8B, a pixel group 700 may include a third photodiodePD3, a third color filter CF3 disposed on the third photodiode PD3, afourth photodiode PD4, a fourth color filter CF4 disposed on the fourthphotodiode PD4, an element isolation layer 710, a pixel circuit region730, a first floating diffusion region FDa, and a second floatingdiffusion region FDb. Hereinafter, differences between a verticalstructure of the pixel group 700 in FIG. 8B and the vertical structureof the pixel group 700 in FIG. 8A will be described.

When a third transfer transistor is turned on according to a controlsignal input to a third transfer gate electrode TG3, a charge generatedby the third photodiode PD3 may move to the first floating diffusionregion FDa. Further, when a fourth transfer transistor is turned onaccording to a control signal input to a fourth transfer gate electrodeTG4, a charge generated by the fourth photodiode PD4 may move to thesecond floating diffusion region FDb.

The first floating diffusion region FDa and the second floatingdiffusion region FDb may be arranged to be spaced apart from each otherin a direction parallel to an upper surface of the pixel circuit region730. The first floating diffusion region FDa and the second floatingdiffusion region FDb may be electrically isolated from each other.Therefore, the first floating diffusion region FDa may store the chargegenerated by the third photodiode PD3, and the second floating diffusionregion FDb may store the charge generated by the fourth photodiode PD4.The first floating diffusion region FDa and the second floatingdiffusion region FDb do not share the charges respectively storedtherein.

An expansion capacitor Cext may be connected to a lower portion of thesecond floating diffusion region FDb through a metal line. The expansioncapacitor Cext may increase capacitance of the second floating diffusionregion FDb. In embodiments, the expansion capacitor Cext may be ametal-insulator-metal (MIM) capacitor or a poly-insulator-poly (PIP)capacitor. In addition, the expansion capacitor Cext may havecapacitance of 1 fF or more and less than 1 pF. FIG. 8B illustrates acase in which the extended capacitor Cext includes upper and lowerelectrodes and a dielectric layer stacked in a direction perpendicularto the upper surface of the pixel circuit region 730. However, in otherembodiments a structure of the extended capacitor Cext may be modifiedin various ways. For example, the expansion capacitor Cext may includethe upper and lower electrodes and the dielectric layer stacked in adirection parallel to the upper surface of the pixel circuit region 730.

A third micro-lens ML3 may be disposed on the third color filter CF3,and a fourth micro-lens ML4 may be disposed on the fourth color filterCF4. The third micro-lens ML3 may focus an optical signal transmittedfrom an object onto the third photodiode PD3. In addition, the fourthmicro-lens ML4 may focus an optical signal transmitted from an objectonto the fourth photodiode PD4.

The third pixel region including the third photodiode PD3 and the fourthpixel region including the fourth photodiode PD4 may constitutedifferent pixels. In an embodiment, the third pixel region mayconstitute a low-illuminance pixel, and the fourth pixel region mayconstitute a high-illuminance pixel. Also, the third pixel region andthe fourth pixel region may constitute the same color pixel region. Forexample, the third pixel region and the fourth pixel region mayconstitute a red pixel region. FIG. 8B illustrates a case in which thecolor filters CF3 and CF4 and the micro-lenses ML3 and ML4 are providedon the third photodiode PD3 and the fourth photodiode PD4, respectively.However, for example, in other embodiments the third photodiode PD3 andthe fourth photodiode PD4 may share one color filter and one micro-lensdisposed thereon.

FIG. 9 illustrates a plan view of the pixel group of FIG. 4 according toembodiments of the inventive concepts. FIG. 10A illustrates across-sectional view taken along line of FIG. 9, and FIG. 10Billustrates a cross-sectional view taken along line IV-IV′ of FIG. 9.

Referring first to FIG. 9, a pixel group 800 may include first to fourthphotodiodes PD1 to PD4, first to fourth transfer gate electrodes TG1 toTG4, and first to fourth floating diffusion regions FD1 to FD4.

The first transfer gate electrode TG1 may be a gate electrode of a firsttransfer transistor connected to the first photodiode PD1, and thesecond transfer gate electrode TG2 may be a gate electrode of a secondtransfer transistor connected to the second photodiode PD2. In addition,the third transfer gate electrode TG3 may be a gate electrode of a thirdtransfer transistor connected to the third photodiode PD3, and thefourth transfer gate electrode TG4 may be a gate electrode of a fourthtransfer transistor connected to the fourth photodiode PD4.

The first to fourth photodiodes PD1 to PD4 may configure differentpixels. In an embodiment, the first to third photodiodes PD1 to PD3 mayconstitute low-illuminance pixels, and the fourth photodiode PD4 mayconstitute a high-illuminance pixel.

The first to third floating diffusion regions FD1 to FD3 may beelectrically connected by metal lines CL1 and CL2. As the first to thirdfloating diffusion regions FD1 to FD3 may be electrically connected, thefirst to third photodiodes PD1 to PD3 constituting the low-illuminancepixel may share each of the floating diffusion regions FD1 to FD3.

The cross-section taken along line of FIG. 9 may be as illustrated inFIG. 10A.

Referring to FIG. 10A, the pixel group 800 may include a firstphotodiode PD1, a first color filter CF1 disposed on the firstphotodiode PD1, a second photodiode PD2, and a second color filter CF2disposed on the second photodiode PD2, an element isolation layer 810, apixel circuit region 830, a first floating diffusion region FD1, and asecond floating diffusion region FD2.

The element isolation layer 810 may isolate a first pixel regionincluding the first photodiode PD1 and a second pixel region includingthe second photodiode PD2, from each other. The element isolation layer810 may extend from lower surfaces of micro-lenses ML1 and ML2 to anupper surface of the pixel circuit region 830. For example, the elementisolation layer 810 may have a full-deep-trench-isolation (FDTI)structure. As the element isolation layer 810 has an FDTI structure,crosstalk due to optical interference between the first pixel region andthe second pixel region may be completely prevented.

The first pixel region including the first photodiode PD1 and the secondpixel region including the second photodiode PD2 may constitutedifferent pixels. In an embodiment, the first pixel region and thesecond pixel region may constitute low-illuminance pixels.

The pixel circuit region 830 may include a first transfer gate electrodeTG1, a second transfer gate electrode TG2, and a plurality of metallines.

When a first transfer transistor is turned on according to a controlsignal input to the first transfer gate electrode TG1, a chargegenerated by the first photodiode PD1 may move to the first floatingdiffusion region FD1. Further, when a second transfer transistor isturned on according to a control signal input to the second transfergate electrode TG2, a charge generated by the second photodiode PD2 maymove to the second floating diffusion region FD2.

The first floating diffusion region FD1 and the second floatingdiffusion region FD2 may be electrically connected to each other througha metal line CL1. As the first floating diffusion region FD1 and thesecond floating diffusion region FD2 are electrically connected to eachother, the first pixel region including the first photodiode PD1 and thesecond pixel region including the second photodiode PD2 may share thefirst floating diffusion region FD1 and the second floating diffusionregion FD2. Therefore, a charge stored in the first floating diffusionregion FD1 and a charge stored in the second floating diffusion regionFD2 may be combined with each other to be used to generate one imagedata.

The first color filter CF1 and the first micro-lens ML1 may besequentially disposed on the first photodiode PD1. In addition, thesecond color filter CF2 and the second micro-lens ML2 may besequentially disposed on the second photodiode PD2. The first micro-lensML1 may focus an optical signal transmitted from an object onto thefirst photodiode PD1, and the second micro-lens ML2 may focus an opticalsignal transmitted from an object onto the second photodiode PD2. Thefirst color filter CF1 and the second color filter CF2 may pass onlyoptical signals having the same wavelength. The first color filter CF1and the second color filter CF2 may include any one of a red colorfilter, a green color filter, or a blue color filter.

The cross-section taken along line IV-IV′ of FIG. 9 may be asillustrated in FIG. 10B.

Referring to FIG. 10B, the pixel group 800 may include a thirdphotodiode PD3, a third color filter CF3 disposed on the thirdphotodiode PD3, a fourth photodiode PD4, a fourth color filter CF4disposed on the fourth photodiode PD4, an element isolation layer 810, apixel circuit region 830, a third floating diffusion region FD3, and afourth floating diffusion region FD4. Hereinafter, differences between avertical structure of the pixel group 800 in FIG. 10B and the verticalstructure 800 in FIG. 10A will be described.

The third pixel region including the third photodiode PD3 and the fourthpixel region including the fourth photodiode PD4 may constitutedifferent pixels. In an embodiment, the third pixel region mayconstitute a low-illuminance pixel, and the fourth pixel region mayconstitute a high-illuminance pixel.

When a third transfer transistor is turned on according to a controlsignal input to a third transfer gate electrode TG3, a charge generatedby the third photodiode PD3 may move to the third floating diffusionregion FD3. In addition, when a fourth transfer transistor is turned onaccording to a control signal input to a fourth transfer gate electrodeTG4, a charge generated by the fourth photodiode PD4 may move to thefourth floating diffusion region FD4.

The third floating diffusion region FD3 and the fourth floatingdiffusion region FD4 may be arranged to be spaced apart from each otherin a direction parallel to an upper surface of the pixel circuit region830. The third floating diffusion region FD3 and the fourth floatingdiffusion region FD4 may be electrically isolated from each other.Therefore, the third floating diffusion region FD3 may store the chargegenerated by the third photodiode PD3, the fourth floating diffusionregion FD4 may store the charge generated by the fourth photodiode PD4,and the third floating diffusion region FD3 and the fourth floatingdiffusion region FD4 do not share the charges respectively storedtherein.

An expansion capacitor Cext may be connected to a lower portion of thefourth floating diffusion region FD4 through a metal line. The expansioncapacitor Cext may increase capacitance of the fourth floating diffusionregion FD4. In an embodiment, the expansion capacitor Cext may be ametal-insulator-metal (MIM) capacitor or a poly-insulator-poly (PIP)capacitor. In addition, the expansion capacitor Cext may havecapacitance of 1 fF or more and less than 1 pF.

The third color filter CF3 and a third micro-lens ML3 may besequentially disposed on the third photodiode PD3. In addition, thefourth color filter CF4 and a fourth micro-lens ML4 may be sequentiallydisposed on the fourth photodiode PD4. The third micro-lens ML3 mayfocus an optical signal transmitted from an object onto the thirdphotodiode PD3. In addition, the fourth micro-lens ML4 may focus anoptical signal transmitted from an object onto the fourth photodiodePD4.

FIG. 11 illustrates a view of a pixel array of an image sensor accordingto embodiments of the inventive concepts. FIG. 12 illustrates a view ofa pixel group that may be included in the pixel array of FIG. 11.

Referring first to FIG. 11, a pixel array 900 of an image sensoraccording to embodiments of the inventive concepts may include aplurality of pixels having an N× M matrix structure (where, N and M arepositive integers). The plurality of pixels of the pixel array 900 mayform a plurality of pixel groups to form a predetermined color pattern.For example, a red-green-green-blue (RGGB) pattern may be formed in thepixel array 900 using first to fourth pixel groups 910 to 940. FIG. 11illustrates that the pixel array 900 has an 8×8 matrix structure andincludes four pixel groups 910 to 940 each consisting of 16 pixels,however in other embodiments a pixel structure of the pixel array 900may be variously modified.

Each of the first and fourth pixel groups 910 and 940 may include atleast one green color filter. The green color filter may be provided foreach pixel G1 to G16, or at least a portion of the plurality of pixelsG1 to G16 may be provided to share one green color filter.

The second pixel group 920 may include at least one red color filter.The red color filter may be provided for each pixel R1 to R16, or atleast a portion of the plurality of pixels R1 to R16 may be provided toshare one red color filter.

The third pixel group 930 may include at least one blue color filter.The blue color filter may be provided for each pixel B1 to B16, or atleast a portion of the plurality of pixels B1 to B16 may be provided toshare one blue color filter.

A specific pixel configuration of each of the first to fourth pixelgroups 910 to 940 may be as illustrated in FIG. 12.

Referring to FIG. 12, a pixel group 1000 may include 16 pixels PXa andPXb having a 4×4 matrix structure. In an embodiment, at least one pixel,among a plurality of pixels included in the pixel group 1000, may be ahigh-illuminance pixel, and remaining pixels thereof may below-illuminance pixels. For example, the pixel group 1000 may includetwo high-illuminance pixels PXb and 14 low-illuminance pixels PXa.

In other embodiments, the number of high-illuminance pixels PXb includedin the pixel group 1000 may be variously changed according to dynamicrange requirements of an imaging device. For example, in order to make adynamic range corresponding to the high-illuminance pixel PXb largerthan a dynamic range corresponding to the low-illuminance pixel PXa, thenumber of high-illuminance pixels PXb included in the pixel group 1000may be appropriately adjusted.

Different than the low-illuminance pixels PXa, in FIG. 12 thehigh-illuminance pixels PXb as shown may further include expansioncapacitors Cext1 and Cext2. Therefore, the high-illuminance pixels PXbmay have a floating diffusion region having capacitance greater thancapacitance of the floating diffusion regions of the low-illuminancepixels PXa. Therefore, in a case that an image sensor operates in a highdynamic range (HDR) mode, since charge loss may be prevented even whenexposure time of the high-illuminance pixels PXb is controlled to be thesame as exposure time of the low-illuminance pixels PXa, image datahaving a relatively high resolution and a relatively high dynamic rangemay be acquired.

The expansion capacitors Cext1 and Cext2 may be disposed in pixelcircuit regions of the high-illuminance pixels PXb. In an embodiment,the expansion capacitors Cext1 and Cext2 may extend in a directionparallel to a substrate, to partially overlap the low-illuminance pixelsPXa. In an embodiment, the expansion capacitors Cext1 and Cext2 mayinclude a metal-insulator-metal (MIM) capacitor, or apoly-insulator-poly (PIP) capacitor. Further, the expansion capacitorsCext1 and Cext2 may have capacitance of 1 fF or more and less than 1 pF.

The high-illuminance pixels PXb may have the same size andcharacteristics as the low-illuminance pixels PXa, except that thehigh-illuminance pixels PXb further include the expansion capacitorsCext1 and Cext2 connected to the floating diffusion region. For example,an area of a light receiving region of the high-illuminance pixels PXbmay be the same as an area of a light receiving region of thelow-illuminance pixels PXa. Since the image sensor may use the pluralityof pixels PXa and PXb having the same size and characteristics togenerate image data, a dark current caused by a difference in size andcharacteristics for each of the plurality of pixels may be removed, andnoise may be reduced.

Although FIG. 12 illustrates that the high-illuminance pixels PXb aredisposed adjacent to a center of the pixel group 1000, in order toincrease light-receiving efficiency of the high-illuminance pixels PXb,a position of the high-illuminance pixels PXb may be variously modified.For example, the high-illuminance pixels PXb may be disposed at aposition spaced a predetermined distance from the center of the pixelgroup 1000 (e.g., an edge region of the pixel group 1000).

FIG. 13 illustrates a plan view of the pixel group of FIG. 12. FIG. 14Aillustrates a cross-sectional view taken along line V-V′ of FIG. 13, andFIG. 14B illustrates a cross-sectional view taken along line VI-VI′ ofFIG. 13.

Referring first to FIG. 13, a pixel group 1100 may include first tosixteenth photodiodes PD1 to PD16, first to sixteenth transfer gateelectrodes TG1 to TG16, and first to fifth floating diffusion regionsFDa to FDe.

The first to sixteenth transfer gate electrodes TG1 to TG16 may be gateelectrodes of first to sixteenth transfer transistors connected to thefirst to sixteenth photodiodes PD1 to PD16.

The first to sixteenth photodiodes PD1 to PD16 may constitute differentpixels. In an embodiment, the first to fifth photodiodes PD1 to PD5 andthe eighth to sixteenth photodiodes PD8 to PD16 may constitutelow-illuminance pixels. Also, the sixth and seventh photodiodes PD6 andPD7 may constitute high-illuminance pixels.

The first, second, and fifth photodiodes PD1, PD2, and PD5 may becommonly connected to the first floating diffusion region FDa. Thethird, fourth, and eighth photodiodes PD3, PD4, and PD8 may be commonlyconnected to the second floating diffusion region FDb. The ninth, tenth,thirteenth, and fourteenth photodiodes PD9, PD10, PD13, and PD14 may becommonly connected to the fourth floating diffusion region FDd. Also,the eleventh, twelfth, fifteenth, and sixteenth photodiodes PD11, PD12,PD15, and PD16 may be commonly connected to the fifth floating diffusionregion FDe.

The sixth and seventh photodiodes PD6 and PD7 may be commonly connectedto the third floating diffusion region FDc.

An expansion capacitor Cext may be disposed below the sixth and seventhphotodiodes PD6 and PD7 constituting high-illuminance pixels. Theexpansion capacitor Cext may be connected to the third floatingdiffusion region FDc to increase capacitance of the third floatingdiffusion region FDc. In an embodiment, the expansion capacitor Cext maya metal-insulator-metal (MIM) capacitor or a poly-insulator-poly (PIP)capacitor, and may have capacitance of 1 fF or more and less than 1 pF.In an embodiment, the expansion capacitor Cext may extend in a directionparallel to a substrate, to partially overlap the low-illuminancepixels.

The cross-section taken along line V-V′ of FIG. 13 may be as illustratedin FIG. 14A.

Referring to FIG. 14A, a pixel group 1100 may include first to fourthphotodiodes PD1 to PD4, an element isolation layer 1110, a pixel circuitregion 1130, and first and second floating diffusion regions FDa andFDb.

Each of the first to fourth photodiodes PD1 to PD4 may constitutedifferent pixel regions. A plurality of pixel regions including thefirst to fourth photodiodes PD1 to PD4 may be isolated from each otherby the element isolation layer 1110. The element isolation layer 1110may optically shield the plurality of pixel regions, to preventcrosstalk due to optical interference. The element isolation layer 1110may extend from lower surfaces of micro-lenses ML1 to ML4 to be disposedbetween the plurality of pixel regions in a vertical direction. Theelement isolation layer 1110 may for example be formed using a trenchprocess, a local-oxidation-of-silicon (LOCOS) process, or the like. Whenthe element isolation layer 1110 is formed by using a trench process,the element isolation layer 1110 may have a deep-trench-isolation (DTI)structure or a shallow-trench-isolation (STI) structure. In anembodiment, the element isolation layer 1110 may have afull-deep-trench-isolation (FDTI) structure extending from lowersurfaces of the micro-lenses ML1 to ML4 to an upper surface of the pixelcircuit region 1130.

The pixel circuit region 1130 may include first to fourth transfer gateelectrodes TG1 to TG4 and a plurality of metal lines.

When a first transfer transistor is turned on according to a controlsignal input to the first transfer gate electrode TG1, a chargegenerated by the first photodiode PD1 may move to the first floatingdiffusion region FDa. In addition, when a second transfer transistor isturned on according to a control signal input to the second transfergate electrode TG2, a charge generated by the second photodiode PD2 maymove to the first floating diffusion region FDa. As a result, the firstfloating diffusion region FDa may store the charges generated by thefirst photodiode PD1 and the second photodiode PD2.

When a third transfer transistor is turned on according to a controlsignal input to the third transfer gate electrode TG3, a chargegenerated by the third photodiode PD3 may move to the second floatingdiffusion region FDb. In addition, when a fourth transfer transistor isturned on according to a control signal input to the fourth transfergate electrode TG4, a charge generated by the fourth photodiode PD4 maymove to the second floating diffusion region FDb. As a result, thesecond floating diffusion region FDb may store the charges generated bythe third photodiode PD3 and the fourth photodiode PD4.

The first floating diffusion region FDa and the second floatingdiffusion region FDb may be electrically connected through the metalline CL. Therefore, the first floating diffusion region FDa and thesecond floating diffusion region FDb may share the charges respectivelystored therein. For example, charges generated by the first to fourthphotodiodes PD1 to PD4 in response to an optical signal incident from anexternal source may be used to generate one image data. Different thanas shown in FIG. 14A, in other embodiments positions and the number ofthe metal lines CL electrically connecting the first floating diffusionregion FDa and the second floating diffusion region FDb may be variouslymodified.

The cross-section taken along line VI-VI′ of FIG. 13 may be asillustrated in FIG. 14B.

Referring to FIG. 14B, a pixel group 1100 may include fifth to eighthphotodiodes PD5 to PD8, an element isolation layer 1110, a pixel circuitregion 1130, and a third floating diffusion region FDc. Hereinafter,differences between a vertical structure of the pixel group 1100 shownin FIG. 14B and the vertical structure of the pixel group 1100 shown inFIG. 14A will be described.

Each of the fifth to eighth photodiodes PD5 to PD8 may configure aplurality of pixels isolated from each other by the element isolationlayer 1110. In an embodiment, each of the fifth photodiode PD5 and theeighth photodiode PD8 may constitute a low-illuminance pixel, and eachof the sixth photodiode PD6 and the seventh photodiode PD7 mayconstitute a high-illuminance pixel.

The sixth photodiode PD6 and the seventh photodiode PD7 may be commonlyconnected to the third floating diffusion region FDc. When a sixthtransfer transistor is turned on according to a control signal input tothe sixth transfer gate electrode TG6, a charge generated by the sixthphotodiode PD6 may move to the third floating diffusion region FDc. Inaddition, when a seventh transfer transistor is turned on according to acontrol signal input to the seventh transfer gate electrode TG7, acharge generated by the seventh photodiode PD7 may move to the thirdfloating diffusion region FDc. As a result, the charges generated by thesixth photodiode PD6 and the seventh photodiode PD7 in response to anoptical signal incident from an external source may be stored in thethird floating diffusion region FDc, and may be used to generate oneimage data.

An expansion capacitor Cext may be connected to a lower portion of thethird floating diffusion region FDc through a metal line. In anembodiment, the expansion capacitor Cext may include ametal-insulator-metal (MIM) capacitor or a poly-insulator-poly (PIP)capacitor.

FIG. 15 illustrates a plan view of the pixel group of FIG. 12 accordingto embodiments of the inventive concepts. FIG. 16A illustrates across-sectional view taken along line VII-VII′ of FIG. 15, and FIG. 16Billustrates a cross-sectional view taken along line VIII-VIII′ of FIG.15. FIG. 17 illustrates a plan view of the pixel group of FIG. 12according to embodiments of the inventive concepts.

Referring first to FIG. 15, a pixel group 1200 may include first tosixteenth photodiodes PD1 to PD16, first to sixteenth transfer gateelectrodes TG1 to TG16, and first to sixteenth floating diffusionregions PD1 to PD16.

The first to sixteenth transfer gate electrodes TG1 to TG16 may be gateelectrodes of first to sixteenth transfer transistors connected to thefirst to sixteenth photodiodes PD1 to PD16.

The first to sixteenth photodiodes PD1 to PD16 may constitute differentpixels. In an embodiment, the first to fifth photodiodes PD1 to PD5 andthe eighth to sixteenth photodiodes PD8 to PD16 may constitutelow-illuminance pixels. Also, the sixth and seventh photodiodes PD6 andPD7 may constitute high-illuminance pixels.

The first to sixteenth photodiodes PD1 to PD16 may be connected to thefirst to sixteenth floating diffusion regions FD1 to FD16, respectively.Different than in FIG. 13, the first to sixteenth photodiodes PD1 toPD16 in FIG. 15 may be respectively connected to different floatingdiffusion regions FD1 to FD16, but the plurality of floating diffusionregions FD1 to FD16 may be divided for high-illuminance andlow-illuminance pixels to be electrically connected to each other, andmay share charges with each other.

The first to fourth floating diffusion regions FD1 to FD4 may beelectrically connected by a first metal line CL1. The first, fifth,ninth, and thirteenth floating diffusion regions FD1, FD5, FD9, and FD13may be electrically connected by a second metal line CL2. The thirteenthto sixteenth floating diffusion regions FD13 to FD16 may be electricallyconnected by a third metal line CL3. The fourth, eighth, twelfth, andsixteenth floating diffusion regions FD4, FD8, FD12, and FD16 may beelectrically connected by a fourth metal line CL4. The ninth, tenth,thirteenth, and fourteenth floating diffusion regions FD9, FD10, FD13,and FD14 may be electrically connected by a plurality of metal lines CL.Also, the eleventh, twelfth, fifteenth, and sixteenth floating diffusionregions FD11, FD12, FD15, and FD16 may be electrically connected by aplurality of metal lines CL. As a result, the first to fifth floatingdiffusion regions FD1 to FD5 and the eighth to sixteenth floatingdiffusion regions FD8 to FD16 may be electrically connected to sharecharges with each other.

In addition, the sixth and seventh floating diffusion regions FD6 andFD7 may be electrically connected by a metal line CL to share charges.

An expansion capacitor Cext may be disposed below the sixth and seventhphotodiodes PD6 and PD7. The expansion capacitor Cext may be commonlyconnected to the sixth and seventh floating diffusion regions FD6 andFD7 to increase capacitance of the sixth and seventh floating diffusionregions FD6 and FD7. In an embodiment, the expansion capacitor Cext maybe a MIM capacitor or a PIP capacitor, and may have capacitance of 1 fFor more and less than 1 pF. In an embodiment, the expansion capacitorCext may extend in a direction parallel to a substrate, to partiallyoverlap the low-illuminance pixels.

The cross-section taken along line VII-VII′ of FIG. 15 may be asillustrated in FIG. 16A.

Referring to FIG. 16A, a pixel group 1200 may include first to fourthphotodiodes PD1 to PD4, an element isolation layer 1210, a pixel circuitregion 1230, and first to fourth floating diffusion regions FD1 to FD4.The pixel circuit region 1230 may include first to fourth transfer gateelectrodes TG1 to TG4 and a plurality of metal lines.

A plurality of pixel regions respectively including the first to fourthphotodiodes PD1 to PD4 may be isolated from each other by the elementisolation layer 1210. The element isolation layer 1210 may opticallyshield the plurality of pixel regions, to prevent crosstalk due tooptical interference. The element isolation layer 1210 may extend in avertical direction from lower surfaces of micro-lenses ML1 to ML4 to bedisposed between the plurality of pixel regions. The element isolationlayer 1210 may be formed using a trench process, alocal-oxidation-of-silicon (LOCOS) process, or the like. When theelement isolation layer 1210 is formed by using a trench process, theelement isolation layer 1210 may have a deep-trench-isolation (DTI)structure or a shallow-trench-isolation (STI) structure. In anembodiment, the element isolation layer 1210 may have afull-deep-trench-isolation (FDTI) structure extending from lowersurfaces of the micro-lenses ML1 to ML4 to an upper surface of the pixelcircuit region 1230.

The first floating diffusion region FD1 and the second floatingdiffusion region FD2 may be electrically connected through a first metalline CL1. Also, the third floating diffusion region FD3 and the fourthfloating diffusion region FD4 may be electrically connected through thefirst metal line CL1. As a result, the first to fourth floatingdiffusion regions FD1 to FD4 may be electrically connected through thefirst metal line CL1 to share charges.

When first to fourth transfer transistors are turned on according to acontrol signal input to each of the first to fourth transfer gateelectrodes TG1 to TG4, charges generated by the first to fourthphotodiodes PD1 to PD4 may move to the first to fourth floatingdiffusion regions FD1 to FD4, respectively. Since the first to fourthfloating diffusion regions FD1 to FD4 may be electrically connected toshare charges, the charges generated by the first to fourth photodiodesPD1 to PD4 in response to an optical signal incident from an externalsource may be used to generate one image data. Different than as shownin FIG. 16A, in other embodiments the number and arrangement of metallines CL electrically connecting the first to fourth floating diffusionregions FD1 to FD4 may be variously modified.

The cross-section taken along line VIII-VIII′ of FIG. 15 may be asillustrated in FIG. 16B.

Referring to FIG. 16B, a pixel group 1200 includes fifth to eighthphotodiodes PD5 to PD8, an element isolation layer 1210, a pixel circuitregion 1230, and sixth and seventh floating diffusion regions FD6 andFD7. Hereinafter, differences between a vertical structure of the pixelgroup 1200 as shown in FIG. 16b and the vertical structure of the pixelgroup 1200 as shown in FIG. 16A will be described.

Each of the fifth to eighth photodiodes PD5 to PD8 may configure aplurality of pixels isolated from each other by the element isolationlayer 1210. In an embodiment, each of the fifth photodiode PD5 and theeighth photodiode PD8 may constitute a low-illuminance pixel, and eachof the sixth photodiode PD6 and the seventh photodiode PD7 mayconstitute a high-illuminance pixel.

When a sixth transfer transistor is turned on according to a controlsignal input to the sixth transfer gate electrode TG6, a chargegenerated by the sixth photodiode PD6 may move to the sixth floatingdiffusion region FD6. Further, when a seventh transfer transistor isturned on according to a control signal input to the seventh transfergate electrode TG7, a charge generated by the seventh photodiode PD7 maymove to the seventh floating diffusion region FD7.

The sixth floating diffusion region FD6 and the seventh floatingdiffusion regions FD7 may be electrically connected through a fifthmetal line CL5. Therefore, the sixth floating diffusion region FD6 andthe seventh floating diffusion region FD7 may share stored charges witheach other. Also, an expansion capacitor Cext may be connected to lowerportions of the sixth and seventh floating diffusion regions FD6 and FD7through a metal line. In an embodiment, the expansion capacitor Cext mayinclude a metal-insulator-metal (MIM) capacitor or a poly-insulator-poly(PIP) capacitor.

As a result, the charges generated by the sixth photodiode PD6 and theseventh photodiode PD7 in response to an optical signal incident from anexternal source may be used to generate one image data.

A method of connecting the plurality of floating diffusion regions FD1to FD16 may be variously modified. For example, referring to FIG. 17, inother embodiments the first and fifth photodiodes PD1 and PD5 may sharethe first floating diffusion region FDa. The second and thirdphotodiodes PD2 and PD3 may share the second floating diffusion regionFDb. The fourth and eighth photodiodes PD4 and PD8 may share the thirdfloating diffusion region FDc. The ninth and thirteenth photodiodes PD9and PD13 may share the fifth floating diffusion region FDe. The tenth,eleventh, fourteenth, and fifteenth photodiodes PD10, PD11, PD14, andPD15 may share the sixth floating diffusion region FDf. Also, thetwelfth and sixteenth photodiodes PD12 and PD16 may share the seventhfloating diffusion region FDg. The first to third floating diffusionregions FDa to FDc and the fifth to seventh floating diffusion regionsFDe-FDg provided to the low-illuminance pixel may be electricallyconnected through a metal line CL to share charges.

Further, the sixth and seventh photodiodes PD6 and PD7 constituting thehigh-illuminance pixels may share the fourth floating diffusion regionFDd.

FIG. 18 illustrates a view of a pixel group that may be included in thepixel array of FIG. 11 according to embodiments of the inventiveconcepts. FIG. 19 illustrates a plan view of the pixel group of FIG. 18.FIG. 20A is a cross-sectional view taken along line IX-IX′ of FIG. 19according to embodiments of the inventive concepts. FIG. 20B is across-sectional view taken along line IX-IX′ of FIG. 19 according toother embodiments of the inventive concepts.

Referring first to FIG. 18, a pixel group 1400 may include 16 pixels PXaand PXb having a 4×4 matrix structure. In an embodiment, at least onepixel, among a plurality of pixels included in the pixel group 1400, maybe a high-illuminance pixel, and remaining pixels thereof may below-illuminance pixels. For example, the pixel group 1400 may includetwo high-illuminance pixels PXb and 14 low-illuminance pixels PXa.

Unlike the pixel group 1000 described with reference to FIG. 12, in thepixel group 1400 of FIG. 18, high-illuminance pixels PXb may be arrangedin a diagonal direction. The position and number of high-illuminancepixels PXb included in the pixel group 1400 may be variously modifiedbased on dynamic range requirements, light-receiving efficiency, or thelike.

Different from the low-illuminance pixels PXa, the high-illuminancepixels PXb may further include expansion capacitors Cext1 and Cext2.Therefore, the high-illuminance pixels PXb may have a floating diffusionregion having capacitance greater than capacitance of the floatingdiffusion regions of the low-illuminance pixels PXa. Therefore, in acase that an image sensor operates in a high dynamic range (HDR) mode,since charge loss may be prevented even when exposure time of thehigh-illuminance pixels PXb is controlled to be the same as exposuretime of the low-illuminance pixels PXa, image data having a relativelyhigh resolution and a relatively high dynamic range may be acquired.

The expansion capacitors Cext1 and Cext2 may be disposed in a pixelcircuit region of the high-illuminance pixels PXb. In an embodiment, theexpansion capacitors Cext1 and Cext2 may extend in a direction parallelto a substrate, to partially overlap the low-illuminance pixel PXa. Inan embodiment, the expansion capacitors Cext1 and Cext2 may include ametal-insulator-metal (MIM) capacitor, or a poly-insulator-poly (PIP)capacitor. In addition, the expansion capacitors Cext1 and Cext2 mayhave capacitance of 1 fF or more and less than 1 pF.

The high-illuminance pixels PXb may have the same size andcharacteristics as the low-illuminance pixels PXa, except that thehigh-illuminance pixels PXb may further include expansion capacitorsCext1 and Cext2 connected to the floating diffusion regions.

Referring to FIG. 19, a pixel group 1500 may include first to sixteenthphotodiodes PD1 to PD16, first to sixteenth transfer gate electrodes TG1to TG16, and first to fifth floating diffusion regions FDa to FDe.

The first to sixteenth transfer gate electrodes TG1 to TG16 may be gateelectrodes of first to sixteenth transfer transistors connected to thefirst to sixteenth photodiodes PD1 to PD16.

The first to sixteenth photodiodes PD1 to PD16 may constitute differentpixels. In an embodiment, the first to fifth photodiodes PD1 to PD5, theseventh to tenth photodiodes PD7 to PD10, and the twelfth to sixteenthphotodiodes PD12 to PD16 may constitute low-illuminance pixels. Also,the sixth and eleventh photodiodes PD6 and PD11 may constitutehigh-illuminance pixels.

The first, second, and fifth photodiodes PD1, PD2, and PD5 may becommonly connected to the first floating diffusion region FDa. The firstfloating diffusion region FDa may store charges generated by the first,second, and fifth photodiodes PD1, PD2, and PD5. The third, fourth,seventh, and eighth photodiodes PD3, PD4, PD7, and PD8 may be commonlyconnected to the second floating diffusion region FDb. The secondfloating diffusion region FDb may store charges generated by the third,fourth, seventh, and eighth photodiodes PD3, PD4, PD7, and PD8. Theninth, tenth, thirteenth, and fourteenth photodiodes PD9, PD10, PD13,and PD14 may be commonly connected to the fourth floating diffusionregion FDd. The fourth floating diffusion region FDd may store chargesgenerated by the ninth, tenth, thirteenth, and fourteenth photodiodesPD9, P10, PD13, and PD14. The twelfth, fifteenth, and sixteenthphotodiodes PD12, PD15, and PD16 may be commonly connected to the fifthfloating diffusion region FDe. The fifth floating diffusion region FDemay store charges generated by the twelfth, fifteenth, and sixteenthphotodiodes PD12, PD15, and PD16. The first, second, fourth, and fifthfloating diffusion regions FDa, FDb, FDd, and FDe may be electricallyconnected by a metal line CL to share charges.

Also, the sixth and eleventh photodiodes PD6 and PD11 may be commonlyconnected to the third floating diffusion region FDc. The third floatingdiffusion region FDc may store charges generated by the sixth andeleventh photodiodes PD6 and PD11. An expansion capacitor Cext may bedisposed below the sixth and seventh photodiodes PD6 and PD7. Theexpansion capacitor Cext may be connected to the third floatingdiffusion region FDc to increase capacitance of the third floatingdiffusion region FDc. In an embodiment, the expansion capacitor Cext maybe a MIM capacitor or a PIP capacitor, and may have capacitance of 1 fFor more and less than 1 pF. In an embodiment, the expansion capacitorCext may extend in a direction parallel to a substrate, to partiallyoverlap the low-illuminance pixels.

The cross-section taken along line IX-IX′ of FIG. 19 may be asillustrated in FIG. 20.

Referring to FIG. 20A, a pixel group 1500 may include first, sixth,eleventh, and sixteenth photodiodes PD1, PD6, PD11, and PD16, an elementisolation layer 1510, a pixel circuit region 1530, and a third floatingdiffusion region FDc. The pixel circuit region 1530 may include first,sixth, eleventh, and sixteenth transfer gate electrodes TG1, TG6, TG11,and TG16 and a plurality of metal lines.

A plurality of pixel regions respectively including the first, sixth,eleventh, and sixteenth photodiodes PD1, PD6, PD11, and PD16 may beisolated from each other by the element isolation layer 1510. Theelement isolation layer 1510 may optically shield the plurality of pixelregions, to prevent crosstalk due to optical interference. The elementisolation layer 1510 may extend in a vertical direction from lowersurfaces of micro-lenses ML1, ML6, ML11, and ML16 to be disposed betweenthe plurality of pixel regions. The element isolation layer 1510 mayhave a deep-trench-isolation (DTI) structure or ashallow-trench-isolation (STI) structure.

When a sixth transfer transistor is turned on according to a controlsignal input to the sixth transfer gate electrode TG6, a chargegenerated by the sixth photodiode PD6 may move to the third floatingdiffusion region FDc. In addition, when a eleventh transfer transistoris turned on according to a control signal input to the eleventhtransfer gate electrode TG11, a charge generated by the eleventhphotodiode PD11 may move to the third floating diffusion region FDc. Thecharges generated by the sixth photodiode PD6 and the eleventhphotodiode PD11 may be stored in the third floating diffusion regionFDc, and may be used to generate one image data.

An expansion capacitor Cext may be connected to a lower portion of thethird floating diffusion region FDc through a metal line. The expansioncapacitor may increase capacitance of the third floating diffusionregion FDc. In an embodiment, the expansion capacitor Cext may include ametal-insulator-metal (MIM) capacitor, or a poly-insulator-poly (PIP)capacitor.

FIG. 20B illustrates an alternative to the cross-section of FIG. 20Aaccording to embodiments of the inventive concepts. Hereinafter,differences between a vertical structure of the pixel group 1500 in FIG.20B and the vertical structure of the pixel group 1500 in FIG. 20A willbe described.

In the embodiment of FIG. 20B, the element isolation layer 1510 may havea full-deep-trench-isolation (FDTI) structure extending from lowersurfaces of the micro-lenses ML1, ML6, ML11, and ML16 to an uppersurface of the pixel circuit region 1530. Instead of the third floatingdiffusion region FDc connectable to the sixth photodiode PD6 and theeleventh photodiode PD11 respectively by way of transfer transistorsincluding the sixth and eleventh transfer gate electrodes TG6 and TG11as shown in FIG. 20A, in FIG. 20B floating diffusion regions FDc1 andFDc2 are provided as separate from each other in a direction parallel tothe substrate. The floating diffusion regions FDc1 and FDc2 arerespectively connectable to the sixth photodiode PD6 and the eleventhphotodiode PD11 respectively by way of transfer transistors includingthe sixth and eleventh transfer gate electrodes TG6 and TG11. Thefloating diffusion regions FDc1 and FDc2 are isolated from each other bythe element isolation region 1510. The floating diffusion regions FDc1and FDc2 may be electrically connected to each other by a metal line CLto share charges. An expansion capacitor Cext may be connected to lowerportions of the floating diffusion regions FDc1 and FDc2 through a metalline CL. The expansion capacitor may increase capacitance of thefloating diffusion regions FDc1 and FDc2. In an embodiment, theexpansion capacitor Cext may include a metal-insulator-metal (MIM)capacitor, or a poly-insulator-poly (PIP) capacitor.

FIG. 21 illustrates a flowchart of an operation method of an imagingdevice according to embodiments of the inventive concepts.

Referring to FIG. 21, an imaging device may perform a high dynamic range(HDR) mode in response to a user input (S110). In addition, the imagingdevice may detect an illumination environment using an illuminancesensor or the like to automatically perform the HDR mode.

In the HDR mode, an image sensor may select any one of a plurality ofrow lines, and may expose at least one first pixel connected to theselected row line for a first time to generate first image data (S120).In an embodiment, the first pixel may be a low-illuminance pixel havinga first conversion gain.

Also, the image sensor may expose at least one second pixel connected tothe selected row line for a second time to generate second image data(S130). In an embodiment, the second pixel may be a high-illuminancepixel having a second conversion gain, lower than the first conversiongain. The high-illuminance pixel may have the same size andcharacteristics as the low-illuminance pixel, except that thehigh-illuminance pixel further includes an expansion capacitor connectedto a floating diffusion. For example, an area of a light receivingregion of the high-illuminance pixel may be the same as an area of alight receiving region of the low-illuminance pixel.

An image signal processor ISP may merge the first image data obtainedfrom the first pixel and the second image data obtained from the secondpixel to generate an object image (S140).

Hereinafter, the operation method of FIG. 21 will be described in detailwith reference to FIG. 22.

FIG. 22 illustrates a waveform diagram of the operation method of FIG.21, which operation is in the HDR mode. In FIG. 22 the horizontal axisrepresents time. In FIG. 22, it is assumed that an image sensoraccording to embodiments of the inventive concepts includes four pixelgroups constituting an RGGB pattern or an RGBW pattern, and each of thepixel groups includes first to fourth pixels. As described above withreference to FIG. 4, first to third pixels may be low-illuminancepixels, and a fourth pixel may be a high-illuminance pixel furtherincluding an expansion capacitor.

Referring to FIG. 22, when a reset transistor (e.g., see FIGS. 5A and5B) of each first to fourth pixels is turned on by reset control signalsRG1 to RG4, a voltage of a floating diffusion region of each of thefirst to fourth pixels may be reset as a predetermined power supplyvoltage. After the voltage of the floating diffusion region of each ofthe first to fourth pixels is reset, when a select transistor of each ofthe first to fourth pixels is turned on by selection control signals SG1to SG4, first to fourth reset voltages V_(R1) to V_(R4) of each of thefirst to fourth pixels may be output to a column line COL through apixel node PN.

After the reset voltages V_(R1) to V_(R4) of each of the first to fourthpixels are output to the column line COL, when a transfer transistor ofeach of the first to fourth pixels is turned on by transfer controlsignals TG1 to TG4, a charge generated by a photodiode of each of thefirst to third pixels, which may be low-illuminance pixels, and a chargegenerated by a photodiode of the fourth pixel, which may be ahigh-illuminance pixel, may respectively move to floating diffusionregions FD. In an embodiment, first exposure time EIT1 of each of thefirst to third pixels may be equal to or longer than second exposuretime EIT2 of the fourth pixel.

In a normal mode automatically controlling exposure time, an imagesensor may sequentially expose the first to fourth pixels to acquire aplurality of image data.

When the select transistor of each of the first to fourth pixels isturned on by the selection control signals SG1 to SG4, first to thirdpixel signals V_(PX1) to V_(PX3) generated by the first to third pixelsand fourth pixel signal V_(PX4) generated by the fourth pixel may beoutput to a column line COL through a pixel node PN, respectively.

The image sensor may generate the image data, based on comparisonresults of the reset voltages V_(R1) to V_(R4) and the pixel signalsV_(PX1) to V_(PX4). In an embodiment, the image sensor may merge andgenerate first to third pixel signals as a single pixel signal by usingan analog binning technique such as floating diffusion sharing or thelike, and may generate low-illuminance image data from the merged andgenerated pixel signals. In addition, in an embodiment, the image sensormay convert first to third pixel signals into digital signals, and mayuse a digital binning technique applying a predetermined weight to theconverted digital signals and summing the weighted digital signals, togenerate low-illuminance image data.

The image sensor may merge high-illuminance image data with thelow-illuminance image data generated in this way to generate a finalobject image.

FIG. 23 illustrates a flowchart of an operation method of an imagingdevice according to embodiments of the inventive concepts.

Referring to FIG. 23, an imaging device may perform a high dynamic range(HDR) mode, based on a user input or an illumination environment (S210).

In the HDR mode, an image sensor may select any one of a plurality ofrow lines, and may expose at least one first pixel connected to theselected row line for first time to generate first image data (S221). Inan embodiment, the first pixel may be a low-illuminance pixel having afirst conversion gain.

Also, the image sensor may expose at least one second pixel connected tothe selected row line for second time, which may be less than or equalto the first time, to generate second image data (S222). In anembodiment, the second pixel may be a high-illuminance pixel having asecond conversion gain, lower than the first conversion gain.

Different from the operation method of FIG. 21, which may merge only thefirst image data and the second image data to generate an object image,the image sensor may sequentially expose all pixels included in theimage sensor to additionally generate third image data (S230). In anembodiment, exposure time of each of the pixels for generating the thirdimage data may be the same.

Thereafter, the image sensor may merge the first to third image data togenerate an object image (S240). Different from the operation method ofFIG. 21, which may merge only high-illuminance image data andlow-illuminance image data to generate an object image, since the imagesensor may additionally merge third image data acquired in the samemanner as a normal mode (that is by sequential exposure), to generate afinal object image, resolution may be further improved.

Hereinafter, the operation method of FIG. 23 will be described in detailwith reference to FIG. 24.

FIG. 24 illustrates a waveform diagram of the operation method of FIG.23, which operation is in the HDR mode. In FIG. 24 the horizontal axisrepresents time. In FIG. 24, it is assumed that an image sensoraccording to embodiments of the inventive concepts includes four pixelgroups constituting an RGGB pattern or an RGGW pattern, and each pixelgroup includes first to fourth pixels. As described above with referenceto FIG. 4, first to third pixels may be low-illuminance pixels, and afourth pixel may be a high-illuminance pixel further including anexpansion capacitor.

Referring to FIG. 24, when a reset transistor (e.g., see FIGS. 5A and5B) of each first to fourth pixels is turned on by reset control signalsRG1 to RG4, a voltage of a floating diffusion region may be reset as apredetermined power supply voltage. After the voltage of the floatingdiffusion region is reset, when a select transistor of each of the firstto fourth pixels is turned on by selection control signals SG1 to SG4,first to fourth reset voltages V_(R1) to V_(R4) of each of the first tofourth pixels may be output to a column line COL through a pixel nodePN.

After the reset voltages V_(R1) to V_(R4) of each of the first to fourthpixels are output to the column line COL, when a transfer transistor ofeach of the first to fourth pixels is turned on by transfer controlsignals TG1 to TG4, a charge generated by a photodiode of each of thefirst to third pixels, which may be low-illuminance pixels, and a chargegenerated by a photodiode of the fourth pixel, which may be ahigh-illuminance pixel, may respectively move to floating diffusionregions FD. In an embodiment, exposure time EIT1 to EIT3 of each of thefirst to third pixels may be equal to or longer than exposure time EIT4of the fourth pixel.

When the select transistor of each of the first to fourth pixels isturned on by the selection control signals SG1 to SG4, first to thirdpixel signals V_(PX1) to V_(PX3) generated by the first to third pixelsand fourth pixel signal V_(PX4) generated by the fourth pixel may beoutput to a column line COL through a pixel node PN, respectively.

The image sensor may generate image data, based on comparison results ofthe reset voltages V_(R1) to V_(R4) and the pixel signals V_(PX1) toV_(PX4). The image sensor may generate first image data from the firstto third pixel signals V_(PX1) to V_(PX3) by applying an analog binningtechnique or a digital binning technique. In an embodiment, the firstimage data may be low-illuminance image data. Also, the image sensor maygenerate second image data from the fourth pixel signal V_(PX4). In anembodiment, the second image data may be high illumination image data.

The reset transistor of each of the first to fourth pixels maythereafter be turned on by the reset control signal RG1 to RG4, to resetthe voltage of the floating diffusion back to a power supply voltage,and reset voltages V_(R1′) to V_(R4′) of each of the first to fourthpixels may be output by the first to fourth selection control signalsSG1 to SG4 to the column line COL through the pixel node PN.

After the reset voltages V_(R1′) to V_(R4′) are output to the columnline COL, when the transfer transistors of each of the first to fourthpixels are sequentially turned on by the transfer control signals TG1 toTG4, the charge generated by the photodiode of each of the first tofourth pixels may respectively move to floating diffusions. Exposuretime EIT5 to EIT7 of each of the first to third pixels, which may below-illuminance pixels, may be equal to or longer than exposure timeEIT8 of the fourth pixel, which may be a high-illuminance pixel.Although FIG. 24 illustrates that the first to fourth pixels aresequentially exposed, in other embodiments for example the first tofourth pixels may be exposed in reverse order.

When the select transistors of each of the first to fourth pixels areturned on by the selection control signals SG1 to SG4, the first tofourth pixel signals V_(PX1′) to V_(PX4′) generated by the first tofourth pixels may be output to a column line through a pixel node,respectively.

The image sensor may generate third image data, based on comparisonresults of the reset voltages V_(R1′) to V_(R4′) and the pixel signalsV_(PX1′) to V_(PX4′). The image sensor may generate third image datafrom the first to fourth pixel signals V_(PX1′) to V_(PX4′) by applyingan analog binning technique or a digital binning technique.

Thereafter, the image sensor may merge the first to third image data togenerate a final object image.

FIG. 25 illustrates a block diagram of an electronic device including animaging device according to embodiments of the inventive concepts.

Referring to FIG. 25, an electronic device 2000 may include an imagingdevice 2010, an input/output device 2020, a memory 2030, a processor2040, and a port 2050. For example, the electronic device 2000 may be asmartphone, a tablet PC, a smart wearable device, or the like.

The imaging device 2010 may include the image sensors described withreference to FIGS. 1 to 24, and may be connected to the processor 2040through a bus 2060 or other communications means.

The input/output device 2020 may include input devices such as forexample a keyboard, a mouse, a touch screen, or the like provided to auser, and output devices such as for example a display, an audio outputunit, or the like.

The memory 2030 may be storage medium for storing data, or multimediadata for operating the electronic device 2000. The memory 2030 mayinclude volatile memory, or nonvolatile memory such as flash memory orthe like. Also, the memory 2030 may include at least one of solid statedrive (SSD), hard disk drive (HDD), and optical drive (ODD) as a storageunit.

The processor 2040 may perform specific operations, commands, tasks, orthe like. The processor 2040 may be a central processing unit (CPU) or amicroprocessor unit (MCU), a system-on-chip (SoC), or the like, and maycommunicate with the imaging device 2010, the input/output device 2020,and the memory 2030, as well as other devices connected to the port2050, through the bus 2060.

The image sensor according to embodiments of the inventive concepts mayprevent blurring of an object image that may occur when the exposuretime may be different by controlling the exposure time of thelow-illuminance pixel and the high-illuminance pixel to be the same.

In addition, the image sensor according to the embodiments of theinventive concepts may prevent the occurrence of a dark current byacquiring an object image using a low-illuminance pixel and ahigh-illuminance pixel having the same size and characteristics.

While example embodiments have been illustrated and described above, itshould be apparent to those skilled in the art that modifications andvariations may be made without departing from the scope of the inventiveconcepts as defined by the appended claims.

What is claimed is:
 1. An imaging device comprising: a pixel arrayconnected to a plurality of row lines and a plurality of column lines,and including a plurality of first pixels having a first conversion gainand a plurality of second pixels having a second conversion gain lowerthan the first conversion gain; a row driver configured to determine aselection row line from among the plurality of row lines; a readoutcircuit configured to respectively obtain a first pixel signal and asecond pixel signal from first pixels and second pixels connected to theselection row line; a column driver configured to generate first imagedata from the first pixel signal and second image data from the secondpixel signal; and an image signal processor configured to generate anobject image from the first image data and the second image data,wherein each of the second pixels includes a floating diffusion node, aground node, and an expansion capacitor connected between the floatingdiffusion node and the ground node, the row driver is configured to setexposure time of the first pixels to be equal to or longer than exposuretime of the second pixels, and an area of a light receiving region ofeach of the first pixels is equal to an area of a light receiving regionof each of the second pixels.
 2. The imaging device of claim 1, whereinthe pixel array comprises a plurality of pixel groups respectivelyincluding two or more first pixels from among the plurality of firstpixels, and one or more second pixels from among the plurality of secondpixels, wherein the plurality of pixel groups have a predetermined colorpattern.
 3. The imaging device of claim 2, wherein in each of theplurality of pixel groups a number of the first pixels is greater than anumber of the second pixels.
 4. The imaging device of claim 2, whereinin each of the plurality of pixel groups, each of the second pixels aredisposed closer to a center of a pixel group than the first pixels. 5.The imaging device of claim 1, wherein the first pixel signalcorresponds to a total amount of charges generated by the first pixelsconnected to the selection row line.
 6. The imaging device of claim 1,wherein the readout circuit is configured to obtain the first pixelsignal by converting pixel signals generated by the first pixelsconnected to the selection row line into digital signals, applying apredetermined weight to the digital signals, and summing the weighteddigital signals.
 7. The imaging device of claim 1, wherein in anenvironment in which external illumination is low, the readout circuitis configured to interpolate the first pixel signal to obtain the secondpixel signal.
 8. The imaging device of claim 1, wherein capacitance ofthe expansion capacitor is 1 fF or more and less than 1 pF.
 9. Animaging device comprising: a pixel array including a plurality of colorpixel groups, wherein each of the plurality of color pixel groupsincluding a plurality of first pixels and at least one second pixel; animage data generator configured to expose the plurality of first pixelsduring a first exposure time to generate first image data, expose the atleast one second pixel during the first exposure time to generate secondimage data, and sequentially expose the plurality of first pixels andthe at least one second pixel during a second exposure time to generatethird image data; and an image signal processor configured to merge thefirst image data, the second image data, and the third image data, togenerate an object image, wherein the image data generator is configuredto generate the first image data by summing pixel signals obtained fromthe plurality of first pixels.
 10. The imaging device of claim 9,wherein conversion gain of the plurality of first pixels is greater thanconversion gain of the at least one second pixel.
 11. The imaging deviceof claim 9, wherein the plurality of first pixels share at least onefloating diffusion node.
 12. The imaging device of claim 9, wherein theimage data generator is configured to convert the pixel signals obtainedby the plurality of first pixels into digital signals, apply apredetermined weight to the digital signals, and sum the weighteddigital signals to generate the first image data.
 13. The imaging deviceof claim 9, wherein each of the plurality of color pixel groups has anN×M matrix structure, wherein N and M are positive integers.
 14. Theimaging device of claim 13, wherein in each of the plurality of colorpixel groups the at least one second pixel is disposed closer to acenter of a color pixel group than the first pixels.
 15. The imagingdevice of claim 14, wherein an area of a light receiving region of eachof the plurality of first pixels is equal to an area of a lightreceiving region of the at least one second pixel.
 16. An image sensorcomprising: a plurality of first pixels including a first floatingdiffusion region disposed in a substrate and a plurality of firstphotodiodes connected to the first floating diffusion region; at leastone second pixel including a second floating diffusion region disposedin the substrate and at least one second photodiode connected to thesecond floating diffusion region, the second floating diffusion regionis disposed adjacent to the first pixels in a direction parallel to anupper surface of the substrate; and an expansion capacitor disposed inthe substrate and connected to the second floating diffusion regionthrough a metal line, wherein the expansion capacitor has a regionoverlapping at least one first pixel among the plurality of first pixelsin a direction parallel to the upper surface of the substrate.
 17. Theimage sensor of claim 16, wherein the plurality of first pixels arearranged to surround the at least one second pixel.
 18. The image sensorof claim 16, wherein a width of each of the plurality of first pixels isequal to a width of the at least one second pixel in a directionparallel to the upper surface of the substrate.
 19. The image sensor ofclaim 16, wherein the expansion capacitor is a metal-insulator-metal(MIM) capacitor.
 20. The image sensor of claim 16, wherein the expansioncapacitor is a poly-insulator-poly (PIP) capacitor.